Discipline Engineering Standard NSW

DisciplineEngineering Standard –NSW

CategorySignalling

Title

Track Circuits

Reference Number

SDS 17 –(RIC Standard: SC 00 13 01 17 SP)

Document Control

Status Date Prepared Reviewed Endorsed Approved

Standards andSystems

StandardsEngineer

GMInfrastructure

Strategy &Performance

SafetyCommittee

Issue 1Revision 2

Mar 05

Refer toReferenceNumber

H Olsen M OwensRefer to minutes

of meeting12/08/04

Engineering Standard–NSWSignalling SDS 17Track Circuits

Issue 1 © Australian Rail Track CorporationRevision 2 This document is uncontrolled when printedMarch 2005 of 30

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About This StandardThis Principle addresses the requirements for providing track circuits anda means of identifying them in the signalling system.



Document HistoryPrimary Source –RIC Standard SC 00 13 01 17 SP Version 3.0

List of Amendments –

ISSUE DATE CLAUSE DESCRIPTION1.1 01/09/2004 Reformatting to ARTC Standard1.2 14/03/2005 Disclaimer Minor editorial change

Footer reformatted



Contents

17 Track Circuits ..........................................................................................................7

17.1 Principle No. 17.1 - Provision And Identification Of Track Circuits .......................................717.1.1 Introduction ...........................................................................................................................717.1.2 Requirements - Provision of Track Circuits ..........................................................................717.1.3 Requirements - Identification of Track Circuits ....................................................................717.1.4 Running Lines ......................................................................................................................7

17.1.4.1 Non Running Lines - Terminal Platforms, Sidings, Yards, & Shunting Necks, etc ......................717.1.4.2 Single Lines ...................................................................................................................................8

17.2 Principle No. 17.2 - Track Circuit Limits And Clearance Points ...........................................1117.2.1 Introduction .........................................................................................................................1117.2.2 Requirements - Track Circuit Limits ...................................................................................1117.2.3 Requirements - Clearance Points ......................................................................................11

17.3 Principle No.17.3 - Location Of Insulated Joints ...................................................................1317.3.1 Introduction .........................................................................................................................1317.3.2 Location of Insulated Joints at Signals without Trainstops ................................................1317.3.3 Location of Insulated Joints at Signals with Trainstops .....................................................1317.3.4 Location of Insulated Joints in Points .................................................................................1317.3.5 Location of Insulated Joints at Level Crossings .................................................................1317.3.6 Location of other Insulated Joints ......................................................................................13

17.4 Principle No. 17.4 –Section Intentionally Left Blank .............................................................15

17.5 Principle No. 17.5 - Section Intentionally Left Blank .............................................................15

17.6 Principle No. 17.6 - Track Circuit Bonding In Non Electrified Territory ...............................1617.6.1 Introduction .........................................................................................................................1617.6.2 Turnouts .............................................................................................................................1617.6.3 Crossovers .........................................................................................................................1617.6.4 Connection of Bonds to Rails .............................................................................................1617.6.5 Polarity of Adjacent Track Circuits .....................................................................................1717.6.6 Long Turnouts and Crossovers ..........................................................................................17

17.7 Principle No.17.7 - Track Circuit Bonding In DC Electrified Territory .................................2217.7.1 Introduction .........................................................................................................................2217.7.2 Turnouts - Single Rail Track Circuits ..................................................................................2217.7.3 Turnouts - Double Rail Track Circuits ................................................................................22

17.7.3.1 50hz AC Track Circuits ...............................................................................................................2217.7.3.2 Jeumont Track Circuits with 4 Wire Receiver ...................................................................................2217.7.3.3 Jeumont Track Circuits with 2 Wire Receiver ...................................................................................2217.7.4 Crossovers - Single Rail Track Circuits ..............................................................................2317.7.5 Crossovers - Double Rail Track Circuits ............................................................................2317.7.6 Connection of Bonds to Rail ...............................................................................................2317.7.7 Polarity or Phasing of Adjacent Track Circuits ...................................................................2317.7.8 Long Turnouts and Crossovers ..........................................................................................23

17.8 Principle No. 17.8 - Tie-In Traction Bonding In DC Electrified Territory ..............................2917.8.1 Introduction .........................................................................................................................2917.8.2 Requirements For The Provision of Tie-In Bonding ...........................................................2917.8.3 Method of Providing Tie-In Bonding ...................................................................................2917.8.4 Tie-In Bonding to Form Connections to Sectioning Huts or Substations ...........................2917.8.5 Cross Bonding ....................................................................................................................29



17.8.6 Track Insulation Plans ....................................................................................................... 2917.8.7 Danger Signs ..................................................................................................................... 30



17 Track Circuits

17.1 Principle No. 17.1 - Provision And Identification Of Track Circuits

17.1.1 Introduction

This Principle addresses the requirements for providing track circuits and a means of identifyingthem in the signalling system.

17.1.2 Requirements - Provision of Track Circuits

Track circuits shall be provided as the fundamental means of train detection and control onregularly used passenger and freight lines.

17.1.3 Requirements - Identification of Track Circuits

A consistent approach to the identification of track circuits shall be adopted to complement thestyle of signalling for which they are provided.

All track circuit identifications shown on plans, diagrams and written in documents shall end withan upper case letter T.

17.1.4 Running Lines

Wherever possible a track circuit identification shall be based on the identification number of therunning signal which leads over it.

For each track circuit past a running signal the identification number shall be suffixed by analphabetic character. Each alphabetic character shall be allocated sequentially in the normaldirection of travel always commencing with the letter A with the exception of the letters E, I and O.

Refer to figure 1.

If a running signal reads over a diverging junction, then in the absence of any other runningsignal numbers on the diverging line a separate series of alphabetic suffixes shall be allocatedsequentially in the normal direction of travel commencing with an appropriate letter.

For example X, Y, Z if there are not more than three track circuits on the diverging line. Refer tofigure 2.

17.1.4.1 Non Running Lines - Terminal Platforms, Sidings, Yards, & Shunting Necks, etc.Wherever possible a track circuit identification shall be based on the identification number of asignal which leads over it. However where this approach does not ideally suit the trackarrangements or there are no suitable signal numbers an identification comprising two or morealphabetic characters describing the particular line shall be allocated.

For each track circuit on its particular line the track circuit identification letters shall be suffixedby an alphabetic character. These shall be allocated sequentially in the direction of travelalways commencing with A. Refer to figure 3.



17.1.4.2 Single Lines

Wherever possible an “in section” track circuit identification shall be based onkilometrage (or mileage) distances from Sydney.

Refer to figure 4.

Track circuits approaching Distant signals shall be identified as UAT and DAT for the up anddown directions respectively with sequential alphabetic suffixes if required. For exampleUBT and UCT.

Refer to figure 4.

Isolated level crossing track circuits shall be identified as UXT, XT, and DXT for the updirection control, crossing control and down direction control track circuits respectively.Refer to figure 5.



17.2 Principle No. 17.2 - Track Circuit Limits And Clearance Points

17.2.1 Introduction

This Principle addresses the requirements for establishing track circuit limits andclearance points between track circuits.

17.2.2 Requirements - Track Circuit Limits

Sufficient track circuits shall be provided to ensure that no track circuit is operating outsideits specified engineering limits and track circuits shall be split where necessary toaccommodate these limits.

In addition to this engineering requirement track circuits shall be split at all running signalsand shunting signals and at sets of points where it is necessary for train movements to beable to pass clear.

Track circuits may also require to be split for specific functions within the signalling system,typically overlaps, level crossings and various forms of approach control arrangements.These track circuit limits shall be determined from other principles and/or by calculationdepending on the functionality to be provided.

17.2.3 Requirements - Clearance Points

Where train movements are to pass clear through points and crossings the minimumdistance between adjacent rails at which a track circuit limit shall be placed is 3 metersoutside the surveyed clearance point.

This point shall be also considered with respect to the maximum length of vehicle overhangand the possibility of vehicles sagging back when the brakes of the train are released. Referto figure 1.

Where standing room in a loop or siding is not critical or where rail head corrosion is likely tooccur due to infrequent use, the insulated joint should be placed 23 metres beyond theclearance point to enable the longest wagon to stand between the insulated joint and theclearance point and also remain clear of the junction. This reduces reliance on one wheel setproviding a good track shunt in these circumstances. This arrangement is not necessary forpoints operated by a ground frame located adjacent to the points. Refer to figure 2.



17.3 Principle No.17.3 - Location Of Insulated Joints

17.3.1 Introduction

This Principle addresses the recommendations for locating insulated joints for various purposes.

17.3.2 Location of Insulated Joints at Signals without Trainstops

Ideally the insulated joints shall be located directly in line with the signal to which they apply andpreferably not more than 2m past the signal. Refer to figure 1.

17.3.3 Location of Insulated Joints at Signals with Trainstops

Ideally the insulated joints shall be located 1.5 to 2.5 m past the trainstop to avoid prematurenormalisation of the trainstop arm in front of an approaching train and not more than 4m pastthe signal to which they apply. Refer to figure 2.

Exceptionally insulated joints may be placed more than 4m past the signal but only where thepermanent way layout prevents closer location. If wrong direction movements require train stopsuppression, then the trainstop must be located within 2.5 m of the blockjoint irrespective of theblockjoint’s relationship to the signal..

17.3.4 Location of Insulated Joints in Points

Wherever possible insulated joints shall be located in the turnout rails of points unless theturnout rails are in the most used route. Refer to figure 3. The insulated joint stagger incrossovers shall be the minimum permitted by the type and angle of V crossing and the trackcentres at the particular location. Care must be taken that any length of rail that will not shunt isminimised.

Exceptionally in heavy haul areas such as the Hunter Valley, insulated joints may be placed in thestraight rails of points where the turnout rails are subject to heavy side loadings.

17.3.5 Location of Insulated Joints at Level Crossings

Wherever possible the insulated joints at which level crossing warning controls cease to operateshall preferably not be located more than 5 m from the edge of the roadway. This is to minimisedelays to road users, notwithstanding the minimum length of track circuit.

17.3.6 Location of other Insulated Joints

These shall be located in accordance with the position shown on the signalling arrangementdrawings which shall be clearly dimensioned.

Note that no track circuit is to be shorter than 15m to avoid being bridged by long vehicles.

In open track, the maximum permitted stagger between insulated joints where there are noimpedance bonds is 2.4 metres. Refer to figure 4.

Where there are impedance bonds, either with double rail track circuits or with double to single railtrack circuits, the maximum stagger shall not exceed 100 mm so that, under failure conditions,the possibility of a feed from one track circuit to the next through a train axle is minimised.



17.4 Principle No. 17.4 –Section Intentionally Left Blank

17.5 Principle No. 17.5 - Section Intentionally Left Blank



17.6 Principle No. 17.6 - Track Circuit Bonding In Non ElectrifiedTerritory

17.6.1 Introduction

This Principle addresses the requirements for the provision of track circuit bonding in nonelectrified territory.

Track circuit bonding is provided to ensure train detection and where practical to providebroken rail detection on main lines and high speed turnouts. The configuration of the bondingat turnouts and crossovers shall be such as to maintain the essential train detection capabilitywhen there are broken rails or otherwise shall be such as to ensure those broken rails fail thetrack circuit.

17.6.2 Turnouts

Insulated joints situated in points (leads) shall be located in the least used or lowest speedleg of the points which will usually be the turnout.

To provide for broken rail and broken bond protection two relays/receivers are to beprovided as shown in figure 1, as required in 17.6.6.

Bonding would only be applied at the one end of the turnout extremity and would in effectbe a series bond.

Contacts of the second track relay are to be wired in series with contacts of the first trackrelay in the relevant circuits or in a track repeat relay circuit.

Track stick proving of signal control relays would only be included in one of the track relays.

Where the extremities of the track circuit beyond the points are of widely different lengthsthen it may not be possible to maintain the relays in fine adjustment and the full parallelbonding arrangement shown in figure 2 may be adopted.

The parallel bonds shall be connected back along the main line as shown to providemaximum broken rail protection on the main line.

17.6.3 Crossovers

Full parallel bonding on crossovers in non-electrified areas shall be provided as shown infigure 3.

The parallel bonds shall be connected back along the main line to provide maximumbroken rail protection on the main line.

17.6.4 Connection of Bonds to Rails

All series and parallel bonds shall be connected to the rails as close as possible to theinsulated joints. This shall be clearly depicted on the track insulation plans.



17.6.5 Polarity of Adjacent Track Circuits

To prevent the incorrect operation of an adjacent track circuit relay due to an insulated jointfailure, track circuits of the same type which abut at an insulated joint shall be of oppositepolarities. Refer to figure 4.

This requirement may be relaxed if at the abutting joints there is:

(I) a track feed on either side, or

(II) in cut section tracks the de-energised track relay isolates the adjacent trackfeed, or

(III) at crossovers with single rail track circuits the failure of a blockjoint applies ashort circuit across the tracks.

Polarity reversal does not apply to audio frequency jointless track circuits.

17.6.6 Long Turnouts and Crossovers

On long motor worked turnouts and crossovers where main aspects are provided for bothroutes, notably high speed turnouts, an additional receiver/relay shall be provided at theblockjoint(s) in the turnout path where the distance from the “V” crossing to the blockjoint(s) exceeds 30 metres. Because of this additional load on the points track circuit the length ofthe track circuit may need to be limited for reliable operation. Where this distance is lessthan 10 metres surface run parallel bonding may be installed, and for distances between 10and 30 metres parallel bonding should be used with the bonds from the blockjoint endburied and connected back along the main line to maximise broken rail detection on themain line.



figure 1

Non electrified - Where the extremity of the track circuit in theturnout does not align with the extremity of the track circuit inthe main line, and it is not practical to place the two track relaysin separate locations.

figure 2

Parallel bonds connected back along the main line

figure 3

Parallel bonds connected back along the main line



PRINCIPLE 17.6

Track Circuit Bonding in Non-Electrified Territory



17.7 Principle No.17.7 - Track Circuit Bonding In DC Electrified Territory

17.7.1 Introduction

This Principle addresses the requirements for the provision of track circuit and/or tractionreturn bonding in DC electrified territory.

Track circuit bonding is provided to ensure train detection and where practical to providebroken rail detection on main lines and high speed turnouts. The configuration of the bondingat turnouts and crossovers shall be such as to maintain the essential train detectioncapability when there are broken rails or otherwise shall be such as to ensure those brokenrails fail the track circuit.

17.7.2 Turnouts - Single Rail Track Circuits

If the traction return is designed for single rail return then, to provide for the broken rail andbroken bond protection at the turnouts, two track relays/receivers shall be provided asshown in figure 1. Bonding should only be applied at one end of the turnout extremity andwill in effect be a series bond.

Contacts of this track relay/receiver re to be wired in series with contacts of the first trackrelay and preferably switch a common track repeat relay which then controls the relevantcircuits.

Track stick proving of signal control relays would only be included in one of the track relays.

17.7.3 Turnouts - Double Rail Track Circuits

17.7.3.1 50hz AC Track CircuitsIf the traction return is designed for double rail return where 50hz AC track circuits are used,then for broken rail and broken bond protection, two track relays shall be provided as shownin figure 2, as required in 17.7.8.

Where the extremities of the track circuit beyond the points are of widely different lengthsthen it may not be possible to maintain the two relays in fine adjustment and full parallelbonding may be adopted as shown in figure 3. This arrangement does not provide brokenrail protection and should be avoided where practical.

17.7.3.2 Jeumont Track Circuits with 4 Wire ReceiverWhere Jeumont 4 wire receivers are used full parallel bonding may be adopted as shown infigure 4. This arrangement does not provide broken rail protection and should be avoidedwhere practical.

17.7.3.3 Jeumont Track Circuits with 2 Wire ReceiverThe arrangement in figure 5, with two receivers is preferred for Jeumont track circuits as it



provides for broken rail protection.



17.7.4 Crossovers - Single Rail Track Circuits

The full parallel bonding arrangement shown in figure 7 shall be adopted for single railtracks on crossovers in electrified areas.

The parallel bond on the signalling rail shall be connected as close as possible to the pointscrossing to provide maximum broken rail protection on the main line.

17.7.5 Crossovers - Double Rail Track Circuits

The full parallel bonding arrangement shown in figure 6 shall be adopted for double railtracks on crossovers in electrified areas.

17.7.6 Connection of Bonds to Rail

All bonds connecting parallel sections of track circuit shall be connected to the rails asclose as possible to the insulated joints as indicated on the track insulation plans toensure that the track circuit shunts satisfactorily at all extremities.

The cross sectional area of all parallel bonds and double-relay Y bonds connecting tractionreturn rails must be sufficient to pass the traction return currents in the area.

17.7.7 Polarity or Phasing of Adjacent Track Circuits

To prevent the incorrect operation of an adjacent track circuit relay due to an insulated jointfailure, track circuits of the same type which abut at an insulated joint shall be of oppositepolarities.

This requirement may be relaxed if at the abutting insulated joints there is :

(I) a track feed on either side, or

(II) in single rail track circuiting over points where an insulated joint failurealways shorts the signalling rail to the common traction rail.

(III) in cut track sections where the de-energised track relay isolates theadjacent track feed.

Polarity reversal does not apply to audio frequency track circuits.

17.7.8 Long Turnouts and Crossovers

On long motor worked turnouts and crossovers where main aspects are provided for bothroutes,notably high speed turnouts, an additional receiver/relay shall be provided at theblockjoint(s) in the turnout path where the distance from the “V” crossing to the blockjoint(s) exceeds 30 metres. Because of this additional load on the points track circuit the length ofthe track circuit may need to be limited for reliable operation. Where this distance is lessthan 10 metres surface run parallel bonding may be installed, and for distances between 10and 30 metres parallel bonding should be used with the bonds from the blockjoint endburied and connected back along the main line to maximise broken rail detection on themain line.



Two Relays

figure 1

Two Relays

figure 2

Double Rail Electrified - Where the trackcircuit extremity on the turnout does notalign with the extremity of the track circuiton the main line. (AC track circuit only)



Parallel bonds - Avoid this arrangement where practical to provide for broken rail protection

figure 3

PRINCIPLE 17.7

Track Circuit Bonding in DC Electrified Territory



Double Rail Electrified: Jeumont with 4 wire Receiver

Parallel Bonds - Avoid this arrangement where practical to providefor broken rail detection(2 wire receiver preferred)

figure 4

Double Rail Electrified: Jeumont with 2 wire Receiver

Two Relays

figure 5

Double Rail Electrified Crossover



Parallel Bonds

figure 6

PRINCIPLE 17.7

Track Circuit Bonding in DC Electrified Territory

figure 7

PRINCIPLE 17.7

Track Circuit bonding in DC Electrified Territory



17.8 Principle No. 17.8 - Tie-In Traction Bonding In DC Electrified Territory

17.8.1 Introduction

This Principle addresses the requirements for the provision of tie-in traction bonds inelectrified territory either between adjacent running lines or where it is necessary to connectthe traction return to a sectioning hut or substation.

17.8.2 Requirements For The Provision of Tie-In Bonding

In multiple track sections to minimise return rail resistance effects it is necessary to distributethe traction return current causing it to flow through all return rails including those on adjacentlines. Tie-in bonding shall be provided for this purpose at suitable intervals along the track,normally between 800m and 1500m.

17.8.3 Method of Providing Tie-In Bonding

For double rail track circuits this shall be achieved by the provision of impedance bondslinked together with cables of the appropriate cross sectional area.

Refer to figure 1.

For single rail track circuits this shall be achieved by connecting the traction return railstogether at the extremities of the single rail to avoid the effects of circulating currents shoulda break occur in a return rail.

17.8.4 Tie-In Bonding to Form Connections to Sectioning Huts or Substations

If it is required to connect the traction rails of double rail track circuits to sectioning hut orsubstation bus bars then tie-in bonding shall be provided as described in Sections 17.8.2and 17.8.3 above.

In addition the tie-in bonding shall be extended to form a connection to the sectioning hut orsubstation bus bars.

Refer to figures 2 and 3.

17.8.5 Cross Bonding

As a general rule, cross bonding should be applied at either end of an interlocking, or groupof turnouts, where the double rail traction return on both (or more) tracks changes to a mix ofsingle / double rail through the interlocking or group of turnouts.

17.8.6 Track Insulation Plans

Full details of all tie-in bonding and all other connections to sectioning huts or substation busbars together with cable types and sizes shall be shown on the track insulation plans.



17.8.7 Danger Signs

Danger signs shall be provided at sectioning huts and substations warning against thedisconnection of tie in bonding.

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